"We just cannot understand what has happened or why it has happened. There are no answers. We are just being asked for time to grieve and to give Shannon a proper burial.

"We are asking people, including the media, to respect our privacy and allow us time to bury Shannon with respect and dignity."

Meanwhile, the grandfather of Shannon Gallagher, the 15-year-old from Donegal who took her own life just two months after her little sister, has spoken out.

His teenage granddaughter was “missing her wee sister” and was “quite unhappy,” James Gallagher told the Irish Independent. When Erin died two months ago Shannon paid tribute to her little sister.

On Tuesday, around midnight, Shannon was found dead near her home in Ballybofey, County Donegal. Her little sister Erin committed suicide in October. Police are investigating claims that the 13-year-old was the victim of a campaign of cyber bullying before she was pushed to suicide.

James Gallagher, the sisters’ grandfather, said, “She was on Facebook to my son last night talking, saying she was quite unhappy.

“She found it quite hard that she was wrapping up presents. She said she was missing her wee sister.

“Whatever happened last night when she was wrapping the presents up for her mum and her wee brother and people.

“Then she wrote on Facebook saying, 'This is the hardest thing I've had to do baby doll'. She called her wee sister baby doll.”

The Donegal Vocational Education Committee, who runs the Finn Valley College in Stranorlar, where both sisters went to school, said they were “trying to find the words and response to the tragedy”.

Chief executive Shaun Purcell said, “The school would still be in crisis mode.”

A spokeswoman for Education Minister Ruairi Quinn said he was "deeply shocked and saddened to learn of Shannon's death". A crisis incident team made up of two psychologists, guidance counsellors, Finn Valley principal Frank Dooley and other teaching staff met to discuss how to support students. Counsellors have been on site since Erin's death in October.

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Purcell said the pupils and staff are “going from hour to hour.”

Ireland’s Health Service Executive (HSE) West released a statement which said, “The HSE extends its deepest sympathies to the family and friends of the deceased.

"The HSE is liaising with the family in relation to this incident and all supports are being made available to provide assistance at this difficult time."

The Mayor of Donegal, Councillor Frank McBrearty, has appealed for privacy for the Gallagher family as the community of Ballybofey attempts to comfort them.

A statement from the Council, reported in the Inishowen News, said, “The Mayor would like to ask that the relevant authorities be given the time and space to review the circumstances of this tragedy so as to allow them to respond in the most appropriate way. He is also asking that the wishes of the family for privacy at this very sad time be respected by all concerned.”

A funeral mass for Shannon will be held at St Mary's Stranorlar, at 11am on Saturday morning followed by burial in Castlefin cemetery.